Анотация: The dynamics of anti-Porphyromonas levii antibody production was assessed by ELISA on a farm endemic for Bovine Necrotic Vulvovaginitis (BNNV) (farm A), one that underwent an outbreak a year previously (farm B) and one in which sporadic cases were observed in the past (farm C). Blood samples were taken 7, 4 and 1 week prior to the expected date of calving and on the first and fourth week after calving. Antibodies were present, pre-partum, in 44.4 percentage and 34.8 percentage of the animals on farm A and B, respectively. The antibody titre increased after calving in animals that developed BNVV by a factor of 3.3 and 2.8, on farms A and B respectively, but remained largely unchanged in animals that did not develop the disease. The frequency of development of BNVV in pre-partum seronegative and seropositive animals was similar: 42.5 percentage and 38.3 percentage, respectively. Antibody titres were significantly higher in animals that developed BNVV than in those that did not develop BNVV